Far-field R wave oversensing in a dual chamber arrhythmia management device: Predisposing factors and practical implications

Initial experience with the Medtronic jewel 7250, the ICD designed to detec t and treat ventricular and supraventricular tachyarrhythmias, is very prom ising. Its effectiveness, however, depends on sensing performance, which ha s not yet been systematically examined. The aim of the study was to determi ne the incidence of, predisposing factors for, and practical implications o f far-field R wave oversensing (FFRWOS) in this dual chamber ICD. During a total followup of 797 months in 48 patients who had the jewel 7250, follow- up strip charts, 12-channel Holter recordings and, in particular cases, Hol ter recordings with intracardiac markers were analyzed for the presence of FFRWOS. FFRWOS was documented in ten (21.3%) patients. Compared to other le ad locations, the right atrial appendage lead position was most frequently associated with FFRWOS (7/27 vs 3/21, P < 0.05). Patients with FFRWOS had s ignificantly more treated and nontreated atrial episodes, many of which wer e judged to have been detected inappropriately. In one case, inappropriate atrial antitachycardia pacing due to R wave oversensing triggered sustained ventricular tachycardia, terminated eventually with a high energy shock. I n dual chamber ICDs, FFRWOS may represent a frequent phenomenon possibly le ading to serious consequences. For atrial leads, a lateral atrial wall posi tion seems to be preferable. In most cases, FFRWOS can be eliminated by opt imization of atrial sensing parameters. Given the possibility of ventricula r proarrhythmia with atrial pacing therapy, the capability of ventricular b ackup defibrillation in respective devices is at least reassuring.